diff --git a/docs/MANUAL-SMOKE-F7.1.md b/docs/MANUAL-SMOKE-F7.1.md
new file mode 100644
index 0000000..c76d9b5
--- /dev/null
+++ b/docs/MANUAL-SMOKE-F7.1.md
@@ -0,0 +1,28 @@
+# Manual smoke — F7.1 intra-diagram mermaid diffing (#22)
+
+Webview SVG rendering isn't covered by automated E2E (sealed sandbox, §6.8), so
+verify the rendered colors by hand once. The host-side augmentation (the styling
+directives injected into the mermaid source) *is* covered by unit + host E2E; this
+smoke confirms mermaid actually paints them.
+
+1. Open a markdown doc with a flowchart:
+
+   ```mermaid
+   flowchart LR
+     A[Start] --> B[Parse]
+     B --> C[Emit]
+   ```
+
+2. Run **Cowriting: Show Track-Changes Preview** (`ctrl+alt+r`). Pin the baseline
+   (**Cowriting: Pin Diff Baseline**).
+3. Edit the diagram: change `B[Parse]` → `B[Parse+Lint]`, add `B --> D[Validate]`,
+   and delete the `B --> C` edge and the `C[Emit]` node.
+4. **Expect** in the preview: `B` outlined amber (changed), `D` green (added),
+   `C` shown as a faded dashed ghost (removed) with a dashed grey ghost edge, and
+   a legend `added · changed · removed` beneath the diagram.
+5. Repeat with a `sequenceDiagram`: add a message (green `rect` band), remove one
+   (grey ghost band, message still visible), confirm a removed participant still
+   appears.
+6. Change a diagram to a `classDiagram` and confirm it still shows the v1
+   whole-block "changed" badge (graceful fallback, INV-30) — no error, no broken
+   render.